Minireview: Prognostic factors and the response to hydroxurea treatment in sickle cell disease

Vital Signs: Use of Recommended Health Care Measures to Prevent Selected Complications of Sickle Cell Anemia in Children and Adolescents — Selected U.S. States, 2019

Introduction

Sickle cell disease (SCD), a group of inherited blood cell disorders that primarily affects Black or African American persons, is associated with severe complications and a >20-year reduction in life expectancy. In 2014, an expert panel convened by the National Heart, Lung, and Blood Institute issued recommendations to prevent or reduce complications in children and adolescents with the most severe SCD subtypes, known as sickle cell anemia (SCA); recommendations included 1) annual screening of children and adolescents aged 2–16 years with transcranial Doppler (TCD) ultrasound to identify those at risk for stroke and 2) offering hydroxyurea therapy to children and adolescents aged ≥9 months to reduce the risk for several life-threatening complications.

Methods

Data from the IBM MarketScan Multi-State Medicaid Database were analyzed. TCD screening and hydroxyurea use were examined for 3,352 children and adolescents with SCA aged 2–16 years and continuously enrolled in Medicaid during 2019. Percentage change during 2014–2019 and variation by health subgroups were assessed. Analyses were stratified by age.

Results

During 2014–2019, TCD screening increased 27% among children and adolescents aged 10–16 years; hydroxyurea use increased 27% among children aged 2–9 years and 23% among children and adolescents aged 10–16 years. However, in 2019, only 47% and 38% of children and adolescents aged 2–9 and 10–16 years, respectively, had received TCD screening and 38% and 53% of children and adolescents aged 2–9 years and 10–16 years, respectively, used hydroxyurea. For both prevention strategies, usage was highest among children and adolescents with high levels of health care utilization and evidence of previous complications indicative of severe disease.

Conclusion and Implications for Public Health Practice

Despite increases since 2014, TCD screening and hydroxyurea use remain low among children and adolescents with SCA. Health care providers should implement quality care strategies within their clinics and partner with patients, families, and community-based organizations to address barriers to delivering and receiving recommended care.

Enhancing the care of patients with sickle cell disease

When typically round red blood cells intermittently elongate and become lodged in the body's microcirculation, this can result in painful vaso-occlusive crises, often referred to as 'sickle cell crises'. The sickling and unsickling process can result in acute pain, chronic anaemia, ischaemic injury and multiple organ damage. One of the main concerns raised by patients with sickle cell disease is the lack of knowledge and understanding of their condition among healthcare professionals in acute care settings. Therefore, this article aims to enhance nurses' understanding of sickle cell disease and the effective management of painful vaso-occlusive crises. While sickle cell disease was traditionally perceived to only occur in people of black African or African-Caribbean ethnic origin, this article seeks to challenge this belief and reconsider sickle cell as a public health concern for all.

Cognitive profile of children with sickle cell anemia compared to healthy controls

OBJECTIVE

To evaluate the cognitive abilities of children and adolescents with sickle cell anemia diagnosed through neonatal screening and to compare them with healthy controls, adjusting the results to their socioeconomic status.

METHODS

Cognitive assessment was performed with the Wechsler WISC-III scale in 64 children and adolescents with sickle cell anemia and in 64 controls matched by gender and age, without the disease and without neurological impairment; socioeconomic status was measured by the Criterion Brasil.

RESULTS

All cognitive scores were lower in the group of patients. The mean overall IQ, Verbal IQ, and Performance IQ were, respectively, 90.95 for the group of patients and 113.97 for the controls (p<0.001); 91.41 for the group of patients and 112.31 for the controls (p<0.001); 92.34 for the group of patients and 113.38 for the controls (p<0.001). Scores for processing speed, distraction resistance, and perceptual organization were also significantly lower in patients. A direct and significant correlation was detected between socioeconomic status and cognitive scores. In the multivariate analysis, for the same socioeconomic status, a child with sickle cell anemia had an average IQ of 21.2 points lower than the mean IQ observed for the controls (p<0.001), indicating that the disease, adjusted for the socioeconomic effect, is a strong predictor of the overall IQ.

CONCLUSION

The cognitive impairment of children with sickle cell anemia is severe and manifests even when the disease effect is adjusted to the socioeconomic status. In the authors' view, such impairment requires an early preventive approach in order to avoid this cognitive damage.

Key Pharmacogenomic Considerations for Sickle Cell Disease Patients

Sickle cell disease (SCD), although a monogenic disease, exhibits a complex clinical phenotype that hampers optimum patient stratification and disease management, especially on hydroxyurea treatment. Moreover, theranostics, the combination of diagnostics to individualize and optimize therapeutic interventions, has not been firmly on the forefront of SCD research and clinical management to date. We suggest that if tailor-made theranostics in SCD is envisaged, pharmacogenomics is anticipated to be the way forward. Herein, we present the current key pharmacogenomic opportunities and challenges in SCD, considering population variation, ethics, and socioeconomic aspects. We focus on pharmacogenomics and pain management, genethics, and cost-effectiveness in SCD. We searched for and synthesized data from PubMed and Google Scholar, and the references from relevant articles, using the keywords "pharmacogenomics," "sickle cell disease," "hydroxyurea," "ethics," "pain management," "morphine metabolism," "opioids," "pharmacogenomics and chronic pain," "cost-effectiveness," and "economic evaluation." Only articles published in English were included. So far, when pharmacogenomics in SCD has been considered, interindividual variability in hydroxyurea response/toxicity has been of primary interest. We underscore the need to extend pharmacogenomic considerations on other therapeutic interventions currently present using a holistic patient-centric approach, and taking disease complications into account as well. Furthermore, we raise awareness toward socioeconomic, ethical, and population differences in the way sickle cell pharmacogenomics might unfold in the future. If pharmacogenomics in SCD is to be used in the clinic in an evidence-based manner, cost-effectiveness and population-specific empirical ethics data are urgently needed.

Influence of Study Design on Developmental and Reproductive Toxicology Study Outcomes

Regulatory studies of developmental and reproductive toxicity (DART) studies have remained largely unchanged for decades, with exposures occurring at various phases of the reproductive cycle and toxicity evaluations at different ages/times depending on the study purpose. The National Toxicology Program has conducted studies examining the power to detect adverse effects where there is a prenatal exposure, but evaluations occur postnatally. In these studies, examination is required of only 1 male and female pup from each litter beyond weaning. This provides poor resolving power to detect rare events (e.g., reproductive tract malformations). If an adverse effect is detected, there is little confidence in the shape of the dose-response curve (and the Benchmark Dose or No Observed Adverse Effect Level [NOAEL]). We have developed a new protocol to evaluate DART, the modified one generation study, with exposure commencing with pregnant animals and retention of 4 males and females from each litter beyond weaning to improve statistical power. These animals can be allocated to specific cohorts that examine subchronic toxicity, teratology, littering, and neurobehavioral toxicity in the same study. This approach also results in a reduction in animal numbers used, compared with individual stand-alone studies, and offers increased numbers of end points evaluated compared with recent Organization for Economic Cooperation and Development proposals.